The present disclosure relates generally to the field of drilling wells and more particularly to downhole drilling motors.
Progressive cavity drilling motors commonly have a helical rotor located within the axial cavity of a non-rotating stator, where the stator is connected to the housing of the motor. As the drilling fluid is pumped down through the motor, the fluid rotates the rotor. The rotor may be coupled to a drill bit through a constant velocity (CV) joint, or, alternatively, through a flexible shaft. The torque available to drive the drill bit may be limited by the torsional strength of the output shaft or the CV joints. In addition, the need for the CV joint or the flexible shaft tends to locate the power section further away from the bit resulting in a longer downhole assembly. Such an assembly may have a torsional and/or lateral natural frequency that is excited by the drilling vibration environment downhole causing vibration damage to downhole equipment in proximity to the motor. Such vibration may accelerate wear on the downhole equipment.